Cameras are known that include a function called continuous autofocus (hereinafter denoted as AF-C), by which a subject as a distinct point is continuously kept in focus. Typically, a digital camera is provided with a display such as a liquid crystal panel. In performing AF-C with such a digital camera, a user can see images output on a display to confirm that the focus remains fixed on a subject even if the subject changes or moves.
The operation of AF-C may be roughly divided into two modes; a minute movement mode and an in-focus position search mode. In the minute movement mode, images are captured while a lens is minutely moved back and forth relative to the current position in an optical axis direction. In the in-focus position search mode, the lens is moved to an in-focus position if the analysis of the images captured by the minutely moved lens suggests an out-of-focus state.
In AF-C performed with a digital camera as described above, the camera minutely moves the lens in order to determine whether it is necessary to search for the in-focus position, even when substantially no changes occur in the position of a subject with respect to the direction of the optical axis of the lens. The minute movements then alter the optical path, causing variations in the angle of view of images output on the display. As a result, a subject that wobbles back and forth is displayed on the display screen, so that the subject appears to vary in size. This creates discomfort for the user who is viewing.
Examples of methods of correcting the variations in the angle of view due to the lens movements are disclosed in JP10-282396A (hereinafter referred to as patent document 1) and JP2008-160622A (hereinafter referred to as patent document 2). Patent document 1 discloses an apparatus for controlling the driving of lenses, including lenses and a position detector that detects the positions of the lenses. Each of the lenses may be independently controlled to eliminate variations in the angle of view. Patent document 2 discloses an imaging apparatus, including lenses and a position detector that detects the positions of the lenses. Each of the lenses may be independently controlled to restrain the variations in the angle of view of output images.